This simple technique gives open-back cabinets a closed-back sound
by Craig Anderton
Closed-back cabinets give a very different sound compared to open-back types: There tends to be more low end, and a “tighter” response. Both have their uses—particularly in the studio, as you can have two tonal options—but if you have only an open-back combo amp, here’s a technique that’s all about getting a closed-back sound out of the same amp. No woodworking required!
The trick is to place your open-back cabinet so the back of the cabinet lies flat on a rug, flush against the floor. Not only does the floor block the cabinet back, but the rug helps absorb some of the sound as well. To mic the amp, you’ll need a boom to point the mic down at the speaker.
Ideally, the input jack will be on the front, and the power cable connection on the back will be recessed (as is the case with the Peavey Windsor amp shown in the picture). This lets the AC line cord feed out the side; if this raises the back up too much off the ground, thus defeating the closed-back effect, a right-angle female AC connector may do the job. Otherwise, you can always cut a small slot in the side of the cabinet as a cable feed-through.
However, there are some important cautions. With many amp designs, ventilation happens through the cabinet back, so putting the cab on its back could block the airflow; this can be particularly problematic with tubes. In this case, you’ll need to monitor temperatures carefully, and record for as short a period of time as possible. Whenever you take a break, move the cab back to its usual position to let it vent for a while—note that even if the amp appears to be performing properly, heat buildup can reduce component life.
Sure, this is one of those stupidly simple ideas, but it works as long as you’re aware of any possible heat build-up—try it when you want to get a different sound out of your open-back cabinet.
Craig Anderton is Editor Emeritus of Harmony Central. He has played on, mixed, or produced over 20 major label releases (as well as mastered over a hundred tracks for various musicians), and written over a thousand articles for magazines like Guitar Player, Keyboard, Sound on Sound (UK), and Sound + Recording (Germany). He has also lectured on technology and the arts in 38 states, 10 countries, and three languages.